Field of the Invention
The present invention relates to an accumulator which is used as a pressure accumulator or a pulsation pressure damping device. The accumulator according to the present invention is used, for example, for a hydraulic piping in a vehicle such as a motor vehicle.
Description of the Conventional Art
The inventors of the present invention have previously proposed an accumulator 51 shown in FIGS. 9 to 11, and the accumulator 51 according to the prior art is structured as follows (refer to Japanese Unexamined Patent Publication No. 2010-112431).
(i) More specifically, the accumulator 51 has an accumulator housing 52 which is provided with an oil port 53 connected to a pressure piping, a stay 54 which is arranged closer to an inner side than the oil port 53 within the housing 52 and is provided with a liquid outlet and inlet 54c in an end surface portion 54b in a leading end of a tubular portion 54a, a bellows 55 which is arranged in an outer peripheral side of the stay 54 and is coupled its fixed end to the oil port 53, a bellows cap 56 which is coupled to a floating end of the bellows 55, a gasket holder 57 which is provided on a surface closer to the stay 54 side in the bellows cap 56, and a discoid gasket 58 which is held by the gasket holder 57 in a state in which the discoid gasket 58 can relatively move in an extending and contracting direction of the bellows 55, as shown in FIG. 9, and a gas chamber 59 is set to an outer peripheral side of the bellows 55 and a liquid chamber 60 is set to an inner peripheral side of the bellows 55.
(ii) At the steady activating time of the pressure piping, the discoid gasket 58 moves in the extending and contracting direction of the bellows 55 together with the bellows cap 56, and balances liquid pressure and gas pressure.
(iii) In the case that the operation of the device stops and the pressure of the pressure piping is extremely lowered (so-called zero-down time), the discoid gasket 58 moves together with the bellows cap 56 and seats on a seat surface 54d of the stay end surface portion 54b so as to close the liquid chamber 60 as shown in FIG. 10. Therefore, the liquid is partially confined in the closed liquid chamber 60, and a state in which the liquid pressure and the gas pressure are balanced is maintained. As a result, the bellows 55 is prevented from being broken by pressure unbalance.
(iv) In the case that the liquid confined in the liquid chamber 60 is expanded due to rise in an atmospheric temperature at the zero-down time, the bellows cap 56 moves toward a position where the liquid pressure and the gas pressure are balanced, with a state in which the discoid gasket 58 seats on the seat surface 54d of the stay end surface portion 54b kept due to difference in the pressure receiving area in both upper and lower surfaces of the discoid gasket 58 as shown in FIG. 11. Therefore, since the state in which the liquid pressure and the gas pressure are balanced is still maintained, the bellows 55 is prevented from being broken.
(v) As a pressure fluctuation absorption mechanism at the liquid expanding time mentioned above, in addition to the gasket holder 57 and the discoid gasket 58, a wave spring 61 and a spring plate 62 are interposed between them, the wave spring 61 and the spring plate 62 elastically energizing the discoid gasket 58 in a direction of pressing the discoid gasket 58 toward the bellows cap 56. A spacer portion 63 is provided on a surface closer to the bellows cap 56 side of the gasket 58, the bellows cap 56 comes into contact with the spacer portion 63 at the zero-down time, and the gas encapsulated in the gas chamber 59 presses the gasket to the stay 54 due to the pressure (the gas pressure) so as to seal. There is a case that the zero-down is carried out with a slight gap provided between the bellows cap 56 and the spacer portion 63. Further, in any event, in the case that the liquid confined in the liquid chamber 60 is expanded from this state, the bellows cap 56 moves toward the position where the liquid pressure and the gas pressure are balanced while compressing the wave spring 61.
Since the accumulator 51 having the above structure has the pressure fluctuation absorption mechanism as mentioned above, the liquid pressure and the gas pressure can be still balanced in the case that the liquid confined in the liquid chamber 60 is expanded at the zero-down time. As a result, the bellows 55 can be prevented from being broken, however, there is room for improvement in the following points.
More specifically, since the pressure fluctuation absorption mechanism has the wave spring 61 and the spring plate 62 in addition to the gasket holder 57 and the discoid gasket 58 as mentioned above, the number of the parts is increased, it takes time and effort in assembling and a cost of the parts is high.
Since it is necessary to elongate the gasket holder 57 at a length of the wave spring 61 and a thickness of the spring plate 62, a problem that the gasket holder 57 interferes with the stay 54 may be caused. Consequently, it is necessary to provide a step portion 54e for clearance in a shoulder portion of the stay 54 as shown in the drawing. As a result, a shape and a manufacturing of the stay 54 are complicated.
Further, the pressure fluctuation absorption mechanism mentioned above can respond to the case that the liquid confined in the liquid chamber 60 is expanded at the zero-down time, however, can not respond to the case that the liquid confined in the liquid chamber 60 is contracted at the zero-down time.